Production process for a thermosetting fiber composite semi-finished product

Abstract

A process for obtaining recyclate from thermosetting materials, comprising the following process steps: providing thermosetting feedstocks to be recycled; crushing the thermosetting feedstocks with a twin-shaft crusher to obtain a large number of fragments; crushing the fragments with a single-shaft crusher to obtain a large number of flakes; and finely grinding the flakes with a grinding device to obtain a recycled powder.

Description

[0001] The present invention relates to a manufacturing process for a thermosetting fiber composite semi-finished product.

[0002] Devices and methods for obtaining fillers from recycled components or from reused thermosets or thermoset fiber composites are already known in the prior art. A disadvantage of these prior art methods and devices is that they cannot produce a uniform and therefore homogeneous recyclate with an average particle diameter of less than 100 µm. Consequently, in the practical application of the recyclate in the production of thermoset plastics, particularly thermoset fiber composites, failures occur in the manufacturing process. These failures can manifest as film tears due to sharp-edged particles during the sheet molding compound (SMC) manufacturing process or as defects in the manufactured parts, leading to a reduction in mechanical properties (notch reduction effect).Furthermore, due to the inhomogeneous nature of the recycled particles, it is not currently possible to produce Class A molded parts using state-of-the-art technology. Because of these disadvantages, the circular economy has not yet been implemented in the field of thermoset plastics.

[0003] From EP 0 443 051 A1, a process for producing a thermosetting molding compound from a glass fiber-polyester composite, in particular SMC, BMC, or DMC, is known. Waste parts from pressed SMC, BMC, or DMC are shredded in a shredder, whereby the glass fiber-polyester composite structure is mechanically broken down. The glass fibers thus obtained are separated from the powdered recycled fraction in a vibrating screen and subjected to a targeted surface treatment. Wetting agents are added to the powdered recycled fraction. In the production of the new thermosetting molding compound, the obtained powdered recycled fraction is incorporated into the resin paste as a recycled filler. The recycled glass fibers largely replace the original glass fibers that would otherwise be required.

[0004] Based on the aforementioned disadvantages of the prior art, the present invention aims to provide an improved manufacturing process for a thermoset fiber composite semi-finished product, wherein the recycled powder used is preferably obtained via processes for producing recycled material from thermoset starting materials, such as, in particular, thermoset fiber composites, which can be used as a substitute component for a mineral filler in the production of a new thermoset plastic or, in particular, a fiber composite semi-finished product with a thermoset or thermoplastic matrix, which can preferably be used as a Class A component.

[0005] According to a first aspect, the present invention relates to a manufacturing process for a thermoset fiber composite semi-finished product comprising the process steps: A) Providing the formulation components for the production of a thermoset matrix material for fiber-reinforced semi-finished products, comprising a filler mixture and a thermoset reactive resin, wherein the filler mixture comprises at least recycled powder from recycled thermoset starting materials, such as, in particular, fiber-reinforced composites, in a weight ratio of 1% to 40% of the total weight of the filler mixture; B) Conveying the formulation components from step A), comprising the filler mixture and the reactive resin, into a dissolver using at least one metering device; C) Mixing the formulation components in the dissolver process using a dissolver disc and / or a double suction toothed disc to obtain a homogeneous resin-filler mixture comprising the recycled powder;D) Applying the resin-filler mixture from step C) to a co-extruded carrier film, wherein the addition of the resin-filler mixture to the carrier film is carried out via a doctor blade box; E) Applying cut fibers, fiber fabrics, fiber mats made of glass fiber or alternative fiber types such as carbon fibers or natural fibers to the resin-filler mixture applied to the carrier film to obtain a fiber-resin-filler semi-finished product; and F) Fulling the fiber-resin-filler semi-finished product to obtain a semi-finished product, wherein the fibers are uniformly encased with the reactive resin and the recycled powder.

[0006] The addition of recycled material can improve the mechanical properties of the matrix. This, in turn, allows for an improvement in the mechanical properties of the manufactured fiber-reinforced composite parts, thereby reducing the amount of glass fibers required.

[0007] In addition to the recycled powder, the filler mixture in process step A) may contain, among other things, the following other formulation components: unsaturated polyester (UP) resins, vinyl ester (VE) resins, unsaturated hybrid resins, styrene, vinyltol, thermoplastic solutions, calcium carbonate as a filler, as well as peroxides, inhibitors, wetting and dispersing additives and pigments.

[0008] Preferably, the recycled powder can be obtained from recycled thermosetting raw materials, such as fiber-reinforced composites, by means of a process comprising the following process steps: A) Providing thermoset feedstocks for recycling; B) Crushing the thermoset feedstocks from process step A) with a twin-shaft crusher to obtain a large number of fragments; C) Crushing the fragments from process step B) with a single-shaft crusher to obtain a large number of flakes; and D) Finely grinding the flakes from process step C) with a grinding device to obtain a recycled powder.

[0009] It is particularly preferred that thermoset fiber composite components are provided as the thermoset starting material to be recycled in process step A).

[0010] The fiber composite components can be, in particular, molded fiber composite parts. These components preferably comprise glass fibers embedded in a cured thermoset matrix material. The sources of the thermoset fiber composite components to be recycled can originate from various sectors; for example, SMC molded parts from boat and shipbuilding, rotor blades from wind turbines, or other molded fiber composite parts can serve as the starting material, which is now to be recycled.

[0011] Within the scope of the present invention, the term "recyclable starting materials" shall be understood to mean any materials, material mixtures, or components that comprise at least a thermoset plastic and preferably reinforcing fibers, such as glass fibers, which are embedded in a thermoset plastic. The recyclable starting materials are, for example, waste products that arise during the production of new parts, such as fiber composite components, as excess sections, etc.However, within the scope of the present process, old fiber composite components or thermoset components can also be used, which, due to aging or destruction, can no longer be used for the intended function and consequently would actually have to be disposed of, and can now be sustainably used in the inventive process for recycling to become a starting material for the production of new thermoset components.

[0012] Within the scope of the present invention, the term "flakes" is used synonymously with the English term "flakes". The flakes can be small, thin objects that may be brittle or exhibit a certain degree of ductility.

[0013] It can be provided that the thermosetting starting materials, such as in particular the fiber composite molded parts in process step B), are broken into fragments with an average edge length in the range of 5 cm to 20 cm.

[0014] Furthermore, it can preferably be provided that in process step C) the fragments are crushed into flakes with an average edge length in the range of 1 to 5 cm, particularly preferably 2.5 cm.

[0015] It can be provided that the fragments are crushed in process step C) using a cutting mill, a single-shaft shredder and / or a hammer mill. According to the invention, a combination of the aforementioned devices can also be used for crushing.

[0016] In process step D), the flakes can be finely ground into recycled powder using an impact mill and / or a ball mill. The flakes can be finely ground into recycled powder at a throughput of 100 kg / h to 1000 kg / h using either the impact mill or the ball mill.

[0017] In particular, it can be provided that the flakes are finely ground using a cryogenic cooling screw with a continuous supply of nitrogen. The use of a cryogenic cooling screw with a continuous supply of nitrogen proves to be particularly advantageous when ductile flakes are to be finely ground.

[0018] It can be provided that the flakes are finely ground in process step D) to an average grain size / particle size of less than 100 µm.

[0019] In particular, it can be provided that thermosetting fiber composite components are supplied as Sheet Molding Compound (SMC) parts as thermosetting starting materials in process step A).

[0020] It can be particularly advantageous to provide for a further process step A0) before process step A), wherein uncured or incompletely cured fiber composite semi-finished products are provided and subsequently the uncured fiber composite semi-finished products are cured to obtain fiber composite parts to be recycled as thermoset starting materials for process step A).

[0021] It can be provided that in process step A0) the uncured fiber composite semi-finished products are positioned over a flat area under an electromagnetic radiation source and are exposed to electromagnetic radiation in the wavelength range of 780 nm to 1 mm to heat the fiber composite semi-finished products, preferably to a surface temperature in the range of 150 °C to 250 °C.

[0022] The SMC material, once cured, can then be crushed and finely ground, similar to cross-linked thermoset molded parts or thermoset raw materials. This process has the advantage of eliminating the need for the complex and CO2-intensive disposal of uncross-linked thermoset materials, and the cured thermoset molded parts can then be recycled.

[0023] Alternatively, it can be provided that in process step A0) the uncured fiber composite semi-finished products are placed in a tempering oven and exposed to a temperature in the range of 80 °C to 200 °C and the fiber composite semi-finished products are cured in the tempering oven for a period of time in the range of 15 to 360 minutes.

[0024] The SMC materials that have thus hardened can subsequently be crushed and finely ground in the same way as the cross-linked thermoset fiber composite molded parts or the thermoset starting materials, thereby avoiding the complex, costly and CO2-intensive disposal of the uncured SMC materials and allowing them to be recycled as filler substitutes.

[0025] According to a second aspect, the present invention relates to a manufacturing process for a Class A fiber composite molded part comprising the process steps according to the first.

[0026] Aspect of the present invention as well as further encompassing the process steps: G) Pressing the semi-finished product from step F) to obtain a fiber composite molded part; H) Applying an in-mould coating layer in the pressing process with subsequent or direct painting; and I) Curing the fiber composite molded part.

Claims

1. A manufacturing method for a thermosetting fiber composite semi-finished product, comprising the following method steps: A) providing the formulation ingredients for manufacturing a thermosetting matrix material for fiber composite semi-finished products comprising a filler mixture and a thermosetting reactive resin, wherein the filler mixture comprises at least recycled powder from recycled thermosetting starting materials, such as in particular fiber composite materials, in a weight ratio of 1% to 40% of the filler weight; B) conveying the formulation ingredients of step A) comprising the filler mixture and the reactive resin into a dissolver with the aid of at least one metering device; C) mixing the formulation ingredients using a dissolver disk and / or a double suction toothed disk in the dissolver process to obtain a homogeneous resin-filler mixture including the added recyclate; D) doctor blade coating of the resin-filler mixture of step C) onto a co-extruded drag film, wherein the resin-filler mixture is added to the drag film via a doctor blade box; E) applying chopped fibers, fiber fabrics, non-crimp fabrics made of glass fiber or alternative fiber types such as carbon fibers or natural fibers to the resin-filler mixture coated with a doctor blade to obtain a fiber-resin-filler semi-finished product; and F) fulling the fiber-resin-filler semi-finished product to obtain a semi-finished product, wherein the fibers are uniformly enclosed with the reactive resin and the recyclate powder.

2. The manufacturing method for a thermosetting fiber composite semi-finished product according to claim 1, wherein the recyclate powder was obtained from recycled thermosetting starting materials, such as in particular fiber composites, by means of a method comprising the following method steps: A) providing thermosetting starting materials to be recycled; B) breaking the thermosetting starting materials of method step A) with a twin-shaft shredder to obtain a plurality of fragments; C) shredding the fragments of method step B) with a single-shaft shredder to obtain a plurality of flakes; and D) fine grinding of the flakes of method step C) with a grinding device to obtain a recyclate powder.

3. The manufacturing method for a thermosetting fiber composite semi-finished product according to claim 2, wherein thermosetting fiber composite components are provided as a thermosetting starting material to be recycled in method step A).

4. The manufacturing method for a thermosetting fiber composite semi-finished product according to claim 2 or 3, wherein in method step B), the thermosetting starting materials are broken to fragments having an edge length in the range from 5 cm to 20 cm.

5. The manufacturing method for a thermosetting fiber composite semi-finished product according to any one of claims 2 to 4, wherein in method step C), the fragments are shredded into flakes having an edge length in the range from 1 cm to 5 cm.

6. The manufacturing method for a thermosetting fiber composite semi-finished product according to one of claims 2 to 5, wherein the fragments are shredded in method step C) using a cutting mill, a single-shaft shredder and / or a hammer mill.

7. The manufacturing method for a thermosetting fiber composite semi-finished product according to one of claims 2 to 6, wherein in method step D), the flakes are finely ground into the recyclate powder using an impact jet mill and / or a ball mill.

8. The manufacturing method for a thermosetting fiber composite semi-finished product according to claim 7, wherein the flakes are finely ground into the recyclate powder at a throughput in the range of 100 kg / h to 1,000 kg / h using the impact jet mill and / or the ball mill.

9. The manufacturing method for a thermosetting fiber composite semi-finished product according to claim 7 or 8, wherein the flakes are finely ground using a cryogenic cooling screw with continuous addition of nitrogen.

10. The manufacturing method for a thermosetting fiber composite semi-finished product according to one of the preceding claims, wherein in method step D), the flakes are finely ground to a grain size in the range of less than 100 µm.

11. The manufacturing method for a thermosetting fiber composite semi-finished product according to one of the preceding claims, wherein in method step A), thermosetting fiber composite parts as sheet molding compound (SMC) parts are provided as thermosetting starting materials.

12. The manufacturing method for a thermosetting fiber composite semi-finished product according to one of the preceding claims, wherein the method before method step A) comprises the following additional method step: AQ) providing uncured or incompletely cured fiber composite semi-finished products and curing the uncured fiber composite semi-finished products to obtain fiber composite parts to be recycled for use as thermosetting starting materials for method step A).

13. The manufacturing method for a thermosetting fiber composite semi-finished product according to claim 12, wherein in method step A0), the uncured fiber composite semi-finished products are positioned flat under an electromagnetic radiation source and exposed to electromagnetic radiation in the wavelength range from 780 nm to 1 mm to heat the fiber composite semi-finished products, preferably to a surface temperature in the range from 150°C to 250°C.

14. The manufacturing method for a thermosetting fiber composite semi-finished product according to claim 12, wherein in method step A0), the uncured fiber composite semi-finished products are introduced into a tempering furnace, and a temperature in the range from 80°C to 200°C is generated in the tempering furnace, and the fiber composite semi-finished products are cured in the tempering furnace for a period of 15-360 minutes.

15. A manufacturing method for a Class A fiber composite molded part comprising the method steps according to one of claims 1 to 14 and further comprising: G) pressing the semi-finished product of step F) to obtain a fiber composite molded part; H) applying an in-mold coating layer in the pressing process with subsequent painting; and I) curing the fiber composite molded part.